Central Composite Design Research Papers (original) (raw)

The extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes is an ongoing subject of study. This is an overview article that compares the microwave-assisted extraction (MAE) and accelerated solvent extraction... more

The extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes is an ongoing subject of study. This is an overview article that compares the microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) techniques. The extraction of CBs by ASE has been optimised taking into account the variation of pressure, temperature and extraction time by means of experimental design and the Simplex approach. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from MAE and Soxhlet extractions.

Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve... more

Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve bioavailability after oral administration. In this study a composite rotational experimental design was used to evaluate the joint influence of five formulation variables: temperature of the aqueous phase, needle gauge, volume of the organic phase, and the amounts of polymer and surfactant on the micromeritic characteristics of the CyA-loaded NP obtained by the method of Fessi et al. The percentage of drug encapsulated in the NP was also evaluated for each formulation, and the yield, which was expressed as the ratio between the experimentally measured quantity of drug in the formulation and the theoretical content, was determined because CyA undergoes surface adsorption. Potential variables such as stirring speed (500 rpm), final drug concentration (100 μg/mL), or injection rates (GRi = 0.379 mL/s) were maintained constant. The ANOVA corresponding to the experimental design showed that the amounts of polymer and surfactant, and the diameter of the needle used in the preparation of NP, significantly affected the percentage of entrapped drug (r2 = 0.8916). The mean particle size, was significantly affected by all the formulation variables tested except for the amount of surfactant dissolved in the external aqueous phase (r2 = 0.9518). Neither the yield (mean value of 99.61%) nor the size distribution parameters (polydispersity and coefficient of variation) presented good correlation coefficients for the equations obtained, although some variables showed statistical significance. A second study was carried out to investigate the effects on the drug-loaded NP characteristics of varying the global injection rates (GRi) for the organic phase into the aqueous medium. The results showed a dramatic decrease in both particle size and drug incorporation in the carrier as the rate of mixing increased. From the results of both the experimental design and the second study, a theoretical model for nanoparticle formation is proposed that considers the most significant variables, and an empirical relationship to predict mean particle size is presented. Thus, particle size can be controlled by the injection rates (GRi), the needle gauge, and the polymer concentration.

Submerged Arc Welding (SAW) is a common arc welding process which is used to join thick and heavy sections. The basic characteristics of this process are high deposition rate, ability to weld thick sections with ease and longer weld runs.... more

Submerged Arc Welding (SAW) is a common arc welding process which is used to join thick and heavy sections. The basic characteristics of this process are high deposition rate, ability to weld thick sections with ease and longer weld runs. The study of weld bead geometry is important, as it determine the stress carrying capacity of a weld. For the same reason, this paper highlights the analysis and study of process parameters: arc Voltage, welding current, travel speed and electrode extension, on the bead geometry response such as, bead height, bead width and bead penetration. Design Expert 8.0 with 4 factors, 5 levels, rotatable Central Composite Design. was used to develop relationship for predicting weld bead geometry, which enables to quantify the direct and interaction effects. Mathematical models prepared for the submerged arc welding of 16mm thick mild steel by using response surface methodology which co relate the process variables with the bead geometry characteristics then ...

Despite significant advances in water based surface coating technology, the presence of surfactants in emulsion polymer binders leads to loss of performance after prolonged immersion in water, relative to solvent based coatings that are... more

Despite significant advances in water based surface coating technology, the presence of surfactants in emulsion polymer binders leads to loss of performance after prolonged immersion in water, relative to solvent based coatings that are free of surfactant impurities. This study begins with water uptake evaluation of a range of emulsion polymer binders. A carboxylated styrene butadiene rubber latex (c-SBR) performed

The Aluminium Metal Matrix Composites (AMMC's) provides high strength and stif ness to the metals, so it is utilised in the applications like robots, high speed rotating shafts, high speed machinery etc. The AMMCsrequires a fabrication... more

The Aluminium Metal Matrix Composites (AMMC's) provides high strength and stif ness to the metals, so it is utilised in the applications like robots, high speed rotating shafts, high speed machinery etc. The AMMCsrequires a fabrication process to improve its mechanical properties. Some of the previous researches has been involved in applying the reinforced AMMC’s in Electrical Discharge Machining (EDM) to analysis its characteristics. In this research study, the hybrid AMMC’s is used in the EDM process to analysis the optimum input conditions. The combination of Al7075, Boron Carbide (3%), and Zirconium dioxide (15%) are utilized for analysing the EDM process. The Stir Casting method is used for fabrication of hybrid AMMC’s. In addition, Orthogonal array is used to analyse the parameters; Tool Wear Rate (TWR), Surface Roughness (SR) and Maximum Material Removal (MRR) rate on the basis of voltage (V), current (I), pulse-on time () and pulse-of time (). By varying the input parametric values like ,,  and , the output performance measures; TWR, SR and MRR are analysed in the experimental section. The experimental analysis shows that the optimal value of the input parameter is V is 60, I is 8.242, TON is 5.01 and TOFF is 6 and has the output parameter of MRR is 0.4613, TWR is 0.0139 and SR is 2.46. The experimental investigation shows that current is most influence parameters af ects the MRR, TWR and SR

Focused ultrasonic-assisted extraction (FUSE) is a new and particular technique based on the cavitation effect. In this work, the focused ultrasound assisted extraction was studied and developed for the extraction of polycyclic aromatic... more

Focused ultrasonic-assisted extraction (FUSE) is a new and particular technique based on the cavitation effect. In this work, the focused ultrasound assisted extraction was studied and developed for the extraction of polycyclic aromatic hydrocarbons from marine sediments and mussel tissues. The variables influencing the extraction (amplitude of the ultrasound pulse, the extraction time and the solvent) were studied by a full factorial design and a central composite design. As a result, flat response surfaces were obtained and the most convenient conditions were 45% of ultrasound amplitude, 120 s of extraction time and 5 mL of acetone. Both accuracy and precision of the method were evaluated by means of two certified reference materials (marine sediment and mussel tissue) and the results were also compared to those obtained by microwave assisted extraction.

In this study, we have investigated the potential of a native bacterial strain isolated from an Iranian oil field for the production of biosurfactant. The bacterium was identified to be Bacillus mycoides by biochemical tests and 16S... more

In this study, we have investigated the potential of a native bacterial strain isolated from an Iranian oil field for the production of biosurfactant. The bacterium was identified to be Bacillus mycoides by biochemical tests and 16S ribotyping. The biosurfactant, which was produced by this bacterium, was able to reduce the surface tension of media to 34 mN/m. Compositional analysis of the produced biosurfactant has been carried out by thin layer chromatography (TLC) and FT-IR. The biosurfactant produced by the isolate was characterized as lipopeptide derivative. Biosurfactant production was optimized by the combination of central composite design (CCD) and response surface methodology (RSM). The factor selected for optimization of growth conditions were pH, temperature, glucose and salinity concentrations. The empirical model developed through RSM in terms of effective operational factors mentioned above was found to be adequate to describe the biosurfactant production. Through the analysis, glucose and temperature were found to be the most significant factors, whereas pH and salinity had less effect within the ranges investigated. A maximum reduction in surface tension was obtained under the optimal conditions of 16.55 g/l glucose concentration, 39.03 °C, 55.05 g/l total salt concentration and medium pH 7.37.

Aiming to obtain rapid fermentations with high ethanol yields and a retention of high final viabilities (responses), a 23 full-factorial central composite design combined with response surface methodology was employed using inoculum size,... more

Aiming to obtain rapid fermentations with high ethanol yields and a retention of high final viabilities (responses), a 23 full-factorial central composite design combined with response surface methodology was employed using inoculum size, sucrose concentration, and temperature as independent variables. From this statistical treatment, two well-fitted regression equations having coefficients significant at the 5% level were obtained to predict the viability and ethanol production responses. Three-dimensional response surfaces showed that increasing temperatures had greater negative effects on viability than on ethanol production. Increasing sucrose concentrations improved both ethanol production and viability. The interactions between the inoculum size and the sucrose concentrations had no significant effect on viability. Thus, the lowering of the process temperature is recommended in order to minimize cell mortality and maintain high levels of ethanol production when the temperature is on the increase in the industrial reactor. Optimized conditions (200 g/l initial sucrose, 40 g/l of dry cell mass, 30 °C) were experimentally confirmed and the optimal responses are 80.8 ± 2.0 g/l of maximal ethanol plus a viability retention of 99.0 ± 3.0% for a 4-h fermentation period. During consecutive fermentations with cell reuse, the yeast cell viability has to be kept at a high level in order to prevent the collapse of the process.